Montreal: we walked or took the subway everywhere: don't miss Notre Dame Basilica or Old Town. We stayed at the Marriott near the port and it was clean, comfortable and had a good breakfast. The food is touted as great, but we thought it was pretty regular. Lots to see and do. We got a little attitude from some of the locals when we asked questions, maybe they have to prove they have a French background ; ), but Montreal is certainly a great city to see.
We rented a car and toured most of the island - saw fox, bald eagles, beautiful beaches, Anne of Green Gables home, we really enjoyed it had great lobster (but it's cheaper and as good in Bar Harbor). Many historical and beautiful homes in Charlottetown.
Halifax - don't miss Peggy's Cove - beautiful drive there. The city is a nice walk with some good restaurants and sites. We've been here several times and always enjoyed it.
This is a great place, best in the fall but quite pretty year round. - We had a GREAT time on Lulu's Lobster boat tour we booked on-line. We learned a lot about lobster trapping, conservation and saw many seals and bald eagles. We enjoyed a walk around town. Lobster was a great deal here and very reasonably priced. Tendering went quickly, but it was a very small ship.